1. Field of the Invention
The present invention relates to power-line-operated electronic ballasts for gas discharge lamps, particularly of a type that comprises a voltage-doubler in combination with a full-bridge inverter having parallel-resonant output circuitry.
2. Description of Prior Art
Power-line-operated electronic inverter-type ballasts having parallel-resonant output circuitry are well known. One such ballast is described in U.S. Pat. No. 4,277,726 to Burke. However, to achieve an adequate degree of safety from electric shock hazard--as is required to permit listing by Underwriters Laboratories--a ballast of this type generally requires the use of an isolation transformer. However, such an isolation transformer adds significantly to the size, weight and cost of the ballast, in addition to substantially reducing efficiency.